2,032 Works

Design, dynamics, and control of micro underwater vehicle systems for autonomous environmental exploration

Eugen Solowjow
This dissertation covers exploration and monitoring of environmental fields with micro underwater vehicles (μAUVs). The design of an underactuated μAUV is presented. Moreover, control concepts are introduced for trajectory tracking and path following. Two methods for underwater self-localization are presented, which are suitable for μAUVs. The first approach is based on time delays of arrival of acoustic signals. The second approach exploits attenuation of electro-magnetic signals in water. Lastly, an information theoretic control method is...

LDV-Nachstrommessungen auf der „Sydney Express"

Jürgen Kux, Thomas Niemeier & Hanno Stöhrmann
LDV-Nachstrommessungen auf der „Sydney Express"

Indien als Herausforderung für "Hidden Champions" : Erfolgsfaktoren der Marktbearbeitung für deutsche Mittelständler

Rajnish Tiwari
In den letzten Jahren ist der Begriff "Hidden Champions" sowohl unter den Managern als auch unter den Forschern der betriebswirtschaftlichen Praxis populär geworden. Als Hidden Champions werden mittelständische Unternehmen bezeichnet, die von der Öffentlichkeit unerkannt zu weltweiten Marktführern avanciert sind. Die bisherige Erfolgsbilanz der Hidden Champions in Indien ist jedoch eher gemischt. Es gibt einige beispielhafte Erfolgsgeschichten. Es gibt aber auch deutsche Hidden Champions in Indien, die entweder nur unterdurchschnittlich von dem Marktwachstum profitieren oder...

In-Form[at]ieren und Wissenschaft : Wilhelm Ostwalds wissenschaftsorganisatorische Aktivitäten und die Technologien der geistigen Arbeit

Thomas Hapke
Der Nobelpreisträger für Chemie und spätere Privatgelehrte Wilhelm Ostwald ist ein Beispiel für einen Naturwissenschaftler, der schon Anfang des 20. Jahrhunderts explizit die Organisation wissenschaftlicher Kommunikation thematisierte und über die Technik wissenschaftliches Arbeiten mit internationalem Fokus nachdachte. Nach einer kurzen Übersicht zu den (biografischen) Voraussetzungen von Ostwalds wissenschaftsorganisatorischen Aktivitäten werden in diesem Text Ostwalds theoretische und praktische Ansätze zum Formieren, Formatieren und Informieren von Wissenschaft und ihrer Medien vorgestellt. Es geht um Tätigkeiten und Handlungen...

Nonlinear vibrations of a cable system with a tuned mass damper under deterministic and stochastic base excitation

Stefan Kaczmarczyk & Radosław Iwankiewicz
This paper investigates a dynamic model of a cable-mass system equipped with an auxiliary mass element to act as a transverse tuned mass damper (TMD). The cable length varies slowly while the system is mounted in a vertical host structure swaying at low frequencies. This results in base excitation acting upon the cable - mass system. The model takes into account the fact that the longitudinal elastic stretching of the cable is coupled with their...

Numerical analysis of propeller-induced higher-order pressure fluctuations on the ship hull

Stephan Berger
Gegenstand der vorliegenden Arbeit ist die Entwicklung und Validierung einer hybriden Simulationsmethode zur Untersuchung propellerinduzierter Druckschwankungen höherer Ordnung in kavitierender Strömung. Es werden zwei Arten von Propellerkavitation berücksichtigt: Schichtkavitation auf den Flügeln des Propellers und Spitzenwirbelkavitation. Dabei stellt sich heraus, dass insbesondere die Interaktion zwischen Schicht- und Spitzenwirbelkavitation zu stärkeren Druckschwankungen höherer Ordnung führen kann. Herzstück der neu entwickelten Methode ist das Paneelverfahren panMARE, welches zur Bestimmung der Propellerumströmung und von Schichtkavitation eingesetzt wird. Darüber...

Analysis of laser ablation of CFRP by ultra-short laser pulses with short wavelength

Claus Emmelmann, Maren Petersen, André Goeke & Marten Canisius
Material processing of carbon fiber-reinforced polymers (CFRP) by means of shape-cutting technologies is state-of-the-art today. These processes still perform in some applications with lack of part quality such as delamination and low processes productivity. Therefore, laser processing by ultra-short laser pulses has a great potential in material ablation of CFRP. Nevertheless laser process parameters have to be adjusted carefully to reduce extension of heat affected zone (HAZ) and its influence on part quality.

Generation of 3D representative volume elements for heterogeneous materials: a review

Swantje Bargmann, Benjamin Klusemann, Jürgen Markmann, Jan Eike Schnabel, Konrad Schneider, Celal Soyarslan & Jana Wilmers
This work reviews state of the art representative volume element (RVE) generation techniques for heterogeneous materials. To this end, we present a systematic classification considering a wide range of heterogeneous materials of engineering interest. Here, we divide heterogeneous solids into porous and non-porous media, with 0 < void volume fraction < 1 and void volume fraction = 0, respectively. Further subdivisions are realized based on various morphological features. The corresponding generation methods are classified into...

Review on the Production of Polysaccharide Aerogel Particles

Kathirvel Ganesan, Tatiana Budtova, Lorenz Ratke, Pavel Gurikov, Victor Baudron, Imke Preibisch, Philipp Niemeyer, Irina Smirnova & Barbara Milow
A detailed study of the production of polysaccharide aerogel (bio-aerogel) particles from lab to pilot scale is surveyed in this article. An introduction to various droplets techniques available in the market is given and compared with the lab scale production of droplets using pipettes and syringes. An overview of the mechanisms of gelation of polysaccharide solutions together with non-solvent induced phase separation option is then discussed in the view of making wet particles. The main...

An adaptive fuzzy dead-zone compensation scheme and its application to electro-hydraulic systems

Wallace Moreira Bessa, Max Suell Dutra & Edwin Kreuzer
The dead-zone is one of the most common hard nonlinearities in industrial actuators and its presence may drastically compromise control systems stability and performance. Due to the possibility to express specialist knowledge in an algorithmic manner, fuzzy logic has been largely employed in the last decades to both control and identification of uncertain dynamical systems. In spite of the simplicity of this heuristic approach, in some situations a more rigorous mathematical treatment of the problem...

PLAU inferred from a correlation network is critical for suppressor function of regulatory T cells

Feng He, Hairong Chen, Michael Probst-Kepper, Robert Geffers, Serge Eifes, Antonio del Sol, Klaus Schughart, An-Ping Zeng & Rudi Balling
Human FOXP3(+)CD25(+)CD4(+) regulatory T cells (Tregs) are essential to the maintenance of immune homeostasis. Several genes are known to be important for murine Tregs, but for human Tregs the genes and underlying molecular networks controlling the suppressor function still largely remain unclear. Here, we describe a strategy to identify the key genes directly from an undirected correlation network which we reconstruct from a very high time-resolution (HTR) transcriptome during the activation of human Tregs/CD4(+) T-effector...

Numerical simulation of deep vibration compaction in abaqus/CEL and MPM

Alexander Chmelnizkij, Sparsha Sinduri Nagula & Jürgen Grabe
A numerical model is set up to compare CEL and MPM simulating the densification of dry sand using the deep vibration compaction method. This compaction method densifies loose sands by means of shear deformation processes imparted by horizontal vibrations of vibrator probe at the required soil depth. Both methods are capable to simulate large deformation without the drawbacks of mesh distortion. A hypoplastic constitutive model is used to characterize the stress-strain behaviour of the sand....

Influence of drayage patterns on truck appointment systems

Ann-Kathrin Lange, Kristof Ole Kühl, Anne Kathrina Schwientek & Carlos Jahn
Truck appointment systems (TAS) are a well-recognized method to smooth the peaks in truck arrivals at seaport container terminals and thereby reduce operation costs for the terminals and waiting times for trucking companies. This study analyzes the influence of different drayage patterns on the success of a TAS at seaport container terminals by means of a discrete event simulation model. These drayage patterns vary in the percentages of transports between container terminals and container terminals...

Logistics Sprawl in São Paulo Metro Area

Leonardo Guerin & José Geraldo Vieira
The location of logistics facilities close to consumers and well-planned transport infrastructure is important for the flow of goods and sustainability in the region.The main purpose of this research is to verify the logistics sprawl in São Paulo Metropolitan Area and to discuss its reasons. To verify the existence of the phenomenon, a sample of logistics companies’ addresses has been selected and the geographic centers of this sample were calculated, using the barycentre of a...

Spectral theory for Schrödinger operators with δ-interactions supported on curves in ℝ³

Jussi Behrndt, Rupert L. Frank, Christian Kühn, Vladimir Lotoreichik & Jonathan Rohleder
The main objective of this paper is to systematically develop a spectral and scattering theory for self-adjoint Schrödinger operators with δ-interactions supported on closed curves in R3. We provide bounds for the number of negative eigenvalues depending on the geometry of the curve, prove an isoperimetric inequality for the principal eigenvalue, derive Schatten–von Neumann properties for the resolvent difference with the free Laplacian, and establish an explicit representation for the scattering matrix.

An energy approach for the active vibration control of an oscillator with two translational degrees of freedom using two auxiliary rotating masses

Richard Bäumer, Richard Terrill & Uwe Starossek
An active mass damper implementing two auxiliary masses rotating about a single axis is presented. This device is used for the vibration control of an oscillator performing translational motion in a plane (two translational degrees of freedom). In a preferred mode of operation, both auxiliary masses rotate with the same constant angular velocity in opposite directions. The resultant of the produced harmonic centrifugal forces is used for the vibration control. The direction of this control...

Metabolic engineering von Clostridium pasteurianum zur Optimierung der Biobutanolproduktion

Rebekka Schmitz
Clostridium pasteurianum is of great industrial interest regarding its substrate utilization and product spectrum. In this study, methods for metabolic engineering of C. pasteurianum, especially transformation and gene deletion, were analyzed and optimized. Optimized strains were generated by overexpression of pyruvate carboxylase and glycerol dehydratase deletion. Butanol production was selectively increased. Furthermore, our results indicate a novel mechanism of redox regulation in C. pasteurianum.

Factors influencing taper failure of modular revision hip stems

Annika Krull, Michael Morlock & Nicholas Bishop
Stem modularity of revision hip implant systems offers the advantage of the restoration of individual patient geometry but introduces additional interfaces, which are subjected to repetitive bending loading and have a propensity for fretting corrosion. The male stem taper is the weakest part of the modular junction due to its reduced cross section compared to the outside diameter of the stem. Taper fractures can be the consequence of overloading in combination with corrosion. The purpose...

Benchmarking of the DMX CO2 capture process

Paul Broutin, Patrick Briot, Sören Ehlers & Alfons Kather
This paper presents the main results of Task 13.4 of the OCTAVIUS project dedicated to the benchmarking of DMX versus MEA 30 wt. % CO2 capture processes. In the introduction are given the main objectives of the FP7 Project OCTAVIUS, which ended in June 2016. In this first part are also presented the main characteristics of the DMX process developed by IFP Energies nouvelles (IFPEN) and licensed by PROSERNAT, which uses a phase change solvent....

Occurrence of micropollutants in the wastewater streams of cruise ships

Lena Westhof, Stephan Köster & Margrit Reich
Nowadays the protection of the marine environment raises increasing academic and public attention. The issue of organic micropollutants is of equally high importance for the marine ecosystems. Maritime vessels are considered to significant sources of micropollutants especially if the ship carries many passengers, which is often true for cruise ships which frequent attractive and sensitive sea areas. The emission pathways for micropollutants include wastewater discharges and sewage sludge disposal. The findings of the German research...

Influence of carbon nanoparticle modification on the mechanical and electrical properties of epoxy in small volumes

Christian Leopold, Till Augustin, Thomas Schwebler, Jonas Lehmann, Wilfried V. Liebig & Bodo Fiedler
The influence of nanoparticle morphology and filler content on the mechanical and electrical properties of carbon nanoparticle modified epoxy is investigated regarding small volumes. Three types of particles, representing spherical, tubular and layered morphologies are used. A clear size effect of increasing true failure strength with decreasing volume is found for neat and carbon black modified epoxy. Carbon nanotube (CNT) modified epoxy exhibits high potential for strength increase, but dispersion and purity are critical. In...

How to use analogies for breakthrough innovations

Katharina Schild, Cornelius Herstatt & Christian Lüthje
Analogies can trigger breakthrough ideas in new product development. Numerous examples demonstrate that substantial innovations often result from transferring problem solutions from one industry or domain to another. For instance, the designers of the new running shoe generation of Nike, “Nike SHOX”, use the same suspension concept like the technologies applied for Formula 1 racing cars, or the biological Lotus-effect led to the development of various self-cleaning surfaces. Academic research on analogical thinking has been...

Molecular simulations of thermodynamic properties for the system α-cyclodextrin/alcohol in aqueous solution

Daniel Markthaler, Julia Gebhardt, Sven Jakobtorweihen & Niels Hansen
Free-energy calculations based on molecular simulations provide access to a wide range of thermodynamic properties such as the solubility and partitioning of a molecule in and between various phases. It is demonstrated how molecular dynamics free-energy simulations may be used to obtain the solubilities of primary alcohols and n-alkanes in water and binding affinities of primary alcohols to α-cyclodextrin. The equivalence of two distinct routes to calculate binding free energies is shown leading to the...

2-phase dynamic simulation of deep sand compaction to reduce liquefaction

Sparsha Sinduri Nagula & Jürgen Grabe
A numerical model of a shallow foundation resting on sand is set up to simulate the liquefaction of partially saturated sand subjected to a confined transient loading. The foundation is observed to undergo large settlements due to liquefaction of sand. In order to analyze the feasibility of deep vibration compaction in liquefaction mitigation, saturated sand was subjected to compaction and later the same compacted sand with foundation was subjected to a confined transient loading. It...

Morphodynamics of wadden sea areas – field measurements and modeling

Thorsten Albers & Nicole von Lieberman
The Wadden Sea areas of the German North Sea coast are affected by intense morphodynamics. Especially in the mouths of the estuaries sedimentation and erosion occur on different temporal and spatial scales and therefore challenge the decision-makers. To satisfy the requirements, which modern maritime traffic demands, a sustainable concept for sediment management has to be developed to grant an economic and ecologic balanced system. To evaluate different actions and their effects, e.g. by means of...

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